NEW CASTLE, Pa. — Nearly a year after a noxious, cat urine-like odor assaulted the nostrils of Western Pennsylvania residents, an area woman’s persistence has led to a less-than-viable explanation from environmental officials.

Lisa DeSantis, who resolved to not let the matter die without an answer, recently contacted the state Department of Environmental Protection (DEP) to find out what, after its investigation, caused the pervasion of that horrible smell through the city’s downtown and beyond last fall.

The answer was that the investigation was “inconclusive,” the DEP said in its report.

A resident of nearby Shenango Township, Pennsylvania, DeSantis attended meetings of the area commissioners on Nov. 24, telling them that she was pursuing an answer. She returned to Tuesday’s meeting with notification from the DEP’s Northwest Regional Office about the conclusions of its probe.

The DEP determined only that a waste containing mesityl oxide or another similar compound had reacted with a sulfur compound under specific conditions somewhere in the city’s sewer system.

The reaction likely created the distinctive “cat urine” odor and allowed an easy pathway within the sewer system for its quick spread over a large area, the DEP report said.

“No specific industry or waste stream could be definitively identified as the exact cause of the odor,” the report concluded.

Mesityl oxide is a colorless, volatile liquid compound with a strong cat urine-like odor. The liquid is used in paint removers and as an insect repellent.

The DEP was first contacted about the smell on Oct. 27 last year, when the strong chemical odors were detected in the area. Other reports were that the smell was strong a few miles southwest in the Mahoningtown, Pennsylvania area near where the city sewage treatment plant is located, and in Union Township, Pennsylvania, over four hours away near Philadelphia.

In the year since the strong odor clasped the area, the mystery of its source resonated nationally with media outlets waiting for answers along with area and state residents.

Wachter writes for The New Castle (Pennsylvania) News.